The present invention relates to electron emission, particularly to electron emitters for low electric fields, and more particularly to an electron emitter composed of a substrate coated with nitrogen-doped, amorphous-diamond which exhibit emissions at very low electric fields.
Reliable electron emission from cold cathodes, at low electric fields, has long been a goal to be achieved, and particularly for applications such as flat-panel emission displays (FEDs), which requires a cathode that emits at low fields to be practical.
Recently, diamond, diamond-like carbon and amorphous-diamond thin films have become of considerable interest for various applications, and have the potential of becoming an important electronic material due to their special properties. These films are hard, with high thermal conductivity and with high electron and hole mobilities, and can be deposited by several known methods. Diamond-like carbon and amorphous-diamond (ie, disordered tetrahedral carbon), which have characteristics similar to diamond, are being developed due to the high cost of diamond. The following articles set forth properties and exemplify prior development efforts relative to amorphous carbon and diamond-like carbon: J. Robertson, "Properties of diamond-like carbon", Surface and Coatings Technology, 50 (1992), pp. 185-203; D. R. McKenzie et al, "Compression-Stress-Induced Formation of Thin-Film Tetrahedral Amorphous Carbon", Physical Review Letters, Vol. 67, No. 6, August 1991, pp. 773-776; C. J. Torng et al, "Structure and bonding studies of C:N thin films produced by rf sputtering method", J. Mater. Res., Vol. 5, No. 11, November 1990, pp. 2490-2496; and D. F. Franceschini et al, "Internal stress reduction by nitrogen incorporation in amorphous carbon thin films", Appl. Phys. Lett. 60 (26), June 1992, pp. 3229-3231. Also, efforts have been directed to the fabrication of amorphous-diamond films because amorphous diamond (a:D) is a hard, electrically insulating, inert and transparent form of carbon. The fabrication of the amorphous diamond films was carried out using a filtered cathodic arc system such as that of U.S. Pat. No. 5,279,723 issued Jan. 18, 1994 to S. Falabella et al. See S. Falabella et al, "Fabrication of amorphous diamond films", Thin Solid Films, 236 (1993) 82-86; and copending U.S. application Ser. No. 08/047,176, filed Apr. 16, 1993, now U.S. Pat. No. 5,474,816, entitled "Fabrication of Amorphous Diamond Films", in the name of S. Falabella.
While these prior efforts have advanced the state of the art relative to various applications for amorphous-diamond films, it has been recognized that amorphous diamond, when properly doped, can lower the field values for electron emission from cold cathodes. Thus, the present invention is directed to an amorphous-diamond electron emitter, basically composed of a substrate coated with nitrogen-doped, amorphous diamond (a:D-N), which exhibits emission at substantially lower fields than the uncoated substrate or the substrate having a coating of un-doped amorphous-diamond. Preliminary tests show a reduction of required field emission from a cold cathode surface of from over 60 volts/micrometer to less than 20 volts/micrometer, a significant reduction.